This invention generally relates to catheters, and particularly intravascular catheters for use in percutaneous transluminal coronary angioplasty (PTCA) or for the delivery of stents.
In a typical PTCA procedure, a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient""s coronary anatomy, to position the balloon of the dilatation catheter within the stenosis to be dilated. The balloon is then inflated with radiopaque liquid at relatively high pressures (generally 4-16 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. Additionally, a stent may be implanted within the artery, typically by delivery to a desired location within the artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter and expansion to a larger diameter by inflation of the balloon.
In rapid exchange type balloon catheters, the catheter has an inflation lumen extending from the proximal end of the catheter to a balloon on a distal shaft section, a distal guidewire port at the distal end of the catheter, a proximal guidewire port located distal to the proximal end of the catheter, and a relatively short guidewire lumen extending therebetween. The distal shaft section defines the guidewire lumen, and a distal portion of the inflation lumen in fluid communication with the proximal portion of the inflation lumen defined by the single lumen proximal shaft section. The rapid exchange junction located at the proximal guidewire port at the transition between the proximal shaft section and the distal shaft section should provide a good transition in flexibility from the relatively stiff proximal shaft section to the relatively flexible distal shaft section to facilitate tracking the catheter within the patient""s tortuous vasculature. One difficulty has been forming a rapid exchange junction with the desired characteristics of flexibility, kink resistance, and pushability (i.e., the ability to transmit force from the proximal end to the distal end of the catheter).
To help meet the desire for a catheter having sufficient pushability and crossability, while maintaining trackability, prior art designs have supplemented polymer catheter shafts with a support mandrel. Other prior art designs have addressed these handling and performance issues by using materials of different stiffness for the proximal and distal portions of the catheter, and employing a high strength metallic proximal shaft section, commonly called a hypotube. To prevent kinking at the junction of these two materials, while maintaining trackability and pushability, some conventional designs have employed reinforcing layers or stiffening wires to bridge the transition in catheter shaft material. Despite these attempts, prior art designs have suffered from various drawbacks relating to these handling and performance issues.
Accordingly, it would be a significant advance to provide a catheter having an improved rapid exchange junction.
The invention is directed to a balloon catheter, and preferably to a rapid exchange type balloon catheter, having a proximal shaft section, and a distal shaft section with an inner tubular member and an outer tubular member, the outer tubular member having a section which is bonded as by fusing or otherwise bonding (i.e., xe2x80x9cthe bonded sectionxe2x80x9d) to the inner tubular member. The bonded section extends along a thickened wall portion of the outer tubular member at the rapid exchange junction. A reinforcing member or tube extends within at least a section of the bonded section of the outer tubular member. In one embodiment, the reinforcing tube extends within at least a section of the thickened wall portion of the outer tubular member. The configuration provides a rapid exchange junction with improved kink resistance and flexibility for excellent trackability, and with a minimal decrease in the size of the inflation lumen at the rapid exchange junction for an improved shortened balloon inflation/deflation time.
The balloon catheter of the invention generally comprises an elongated shaft having the proximal shaft section and distal shaft section, an inflation lumen, a guidewire receiving lumen extending in the distal shaft section, and a balloon on the distal shaft section with an interior in fluid communication with the inflation lumen. The proximal shaft section defines a proximal portion of the inflation lumen, and is preferably a metallic tubular member such as a hypotube, although high strength polymers such as polyetheretherketone (PEEK), and polyamide may alternatively be used. The outer tubular member of the distal shaft section defines a distal portion of the inflation lumen in fluid communication with the proximal shaft section and the balloon. The inner tubular member within the distal portion of the inflation lumen defines the guidewire lumen in fluid communication with a guidewire distal port at the inner tubular member distal end and a guidewire proximal port at the inner tubular member proximal end.
As a rapid exchange type catheter, the proximal guidewire port is located in the distal shaft section, distal to the proximal end of the catheter shaft, and preferably a relatively short distance from the balloon and a relatively long distance from the proximal end of the catheter. The proximal guidewire port at the rapid exchange junction is formed by placing the inner tubular member through a hole cut in the outer tubular member side wall, and then bonding part of the circumference of the inner tubular member to the outer tubular member to form the bonded section. The bonded section forms the transition between the single lumen proximal portion of the shaft, and the distal portion of the shaft having the guidewire lumen and the distal portion of the inflation lumen.
In a presently preferred embodiment, the bonded section is formed by thermally bonding (i.e., fusing) the inner tubular member to the outer tubular member by applying heat to melt the polymeric material and fuse the members together. However, the bonded section can be formed by adhesively bonding or a combination of adhesively bonding and thermally bonding the inner and outer members together. Although discussed below primarily in terms of the preferred, fusion bonded embodiment in which the bonded section consists of a fused section, it should be understood that the discussion below also applies to the embodiments in which the bonded section is formed in whole or in part by methods other than fusion bonding. In a presently preferred embodiment, the fused section has a relatively short length, which, in one embodiment, extends from the proximal end of the inner tubular member to a location proximal to the distal end of the outer tubular member. The fused section is preferably formed by locally applying the heat in a focused manner to just the portion of the shaft extending from the guidewire proximal port distally about 1 cm or less. In a presently preferred embodiment, the fused section has a length of about 0.1 to about 1 cm. As a result, the transition formed by the fused section at the rapid exchange junction provides a minimal decrease in the overall size of the inflation lumen as a result of the junction, to thereby minimize the balloon inflation/deflation times.
The thickened wall portion of the outer tubular member is fused to the inner tubular member to form at least a portion of the fused section of the outer tubular member. The thickened wall portion has an inner periphery with a first segment which is bonded to part of an outer surface of the inner tubular member and which extends around part of the inner periphery of the thickened wall portion, and a second segment which is not bonded to the inner tubular member and which extends around the remaining part of the inner periphery of the thickened wall portion of the outer tubular member. In one embodiment, about 10% to about 95%, preferably about 10% to about 70%, and more specifically about 10% to about 50% of an outer periphery (extending around part of the circumference) of the inner tubular member is bonded to the thickened wall portion of the outer tubular member to form the first segment of the inner periphery of the thickened wall portion (i.e., it extends around about 36 to about 320 degrees, preferably about 36 to about 250 degrees of a 360xc2x0 outer periphery of the inner tubular member).
The reinforcing tube within the fused section extends within the outer tubular member of the distal shaft section without necessarily being bonded, e.g., fused or adhesively bonded, thereto. For example, the reinforcing tube can be friction fit within the outer tubular member. Alternatively, part or all of the length of the reinforcing tube can be bonded to the outer tubular member. In one embodiment, at least the distal end of the reinforcing tube is not bonded to the distal outer tubular member, for increased flexibility at the rapid exchange junction. The reinforcing tube is preferably formed of a polymeric material selected from the group consisting of PEEK, polyimide, and other high modulus engineering thermoplastic/thermoset polymers such as polytetrafluoroethylene (PTFE), e.g., TEFLON. The inflation lumen extending within the thickened wall portion of the outer tubular member may be defined by the reinforcing tube extending therein, in which case the second segment of the inner periphery of the outer tubular member thickened wall portion is in contact with the reinforcing tube. In an alternative embodiment, the inflation lumen extending within the thickened wall portion of the outer tubular member is defined by the thickened wall portion itself, in which case the distal end of the reinforcing tube is located proximal to the distal end of the thickened wall portion of the outer tubular member.
The thus formed distal shaft section provides a distal subassembly which can be attached to any type of proximal shaft section, typically by adhesive or fusion bonding the proximal end of the outer tubular member to the distal end of a desired proximal shaft section. In one embodiment, the proximal end of the outer tubular member and the reinforcing tube therein are bonded to the distal end of the proximal shaft section.
The catheter of the invention has excellent ability to track within the patient""s tortuous vasculature due to the improved rapid exchange junction. The fused section of the outer tubular member, with at least a section of the reinforcing tube extending therein and formed at least in part by the thickened wall portion of the outer tubular member, provides a rapid exchange junction with high pushability and flexibility. Moreover, the rapid exchange junction has a short length, which consequently provides for an improved, minimized inflation/deflation duration. These and other advantages of the invention will become more apparent from the following detailed description and drawings.